Performance evaluation of nonlinear algorithms with line‐search for partitioned coupling techniques for fluid–structure interactions

Recently tightly coupled partitioned iterative methods have drawn a great deal of attention due to easy implementation and encapsulation features, and many nonlinear algorithms have been proposed so far. However, their practical performances have not been well understood yet. This paper describes the intensive parametric study on convergence and stability performances of four kinds of nonlinear algorithms with line‐search techniques for partitioned iterative methods of steady/unsteady fluid–structure interaction (FSI) problems. Here we choose three typical FSI problems as test problems, i.e. (1) Collapsible channel as a steady problem, (2) Cavity with flexible bottom membrane and (3) Channel with flexible wall as unsteady problems. Efficiency and robustness dependency of those nonlinear algorithms on physical parameters such as degree of nonlinearity, added mass effect, time step, and control parameters peculiar to each algorithm are clarified. Through those tests, we demonstrate that the Line extrapolation method and Broyden method with Backtrack line‐search technique show good performances in both stability and efficiency.